In this work, brief history of computer vision is shown. The focus is on the deep convolutional neural networks. Two systems for people detection and tracking are built and tested: first one is Viola-Jones algorithm based on Haar features cascades, and YOLO (You Only Look Once) algorithm, one of the best state-of-the-art algorithms for object detection based on deep convolutional neural networks. Following that, numerical results are expressed from the classifiers, their performance is evaluated and misclassified examples and situations are briefly discussed.